1. Field of Invention
The present invention relates to measuring methods and apparatuses and, more particularly, is directed towards methods and apparatuses for measuring minute quantities of antigens, antibodies and other substances.
2. Description of the Prior Art
In recent years, various methods and apparatuses have been designed for measuring minute quantities of antigens in biological samples. An antigen is an agent that stimulates the formation of a corresponding antibody and bindingly reacts therewith. An antibody is a member of a special class of serum proteins, referred to as immunoglobulins, which is formed as a response to an antigen and reacts specifically with it. Antibody-antigen reactions have a specificity comparable to that of enzymes. Generally, antibody or antigen assaying methods are based on these binding reactions which usually cause precipitation or agglutination. Often times, the precipitation or agglutination is visible to the naked eye. However, analysis of smaller concentrations require sensitive instrumentation.
At the cellular level, an antigen can be detected by treatment with a solution of its specific antibody molecules which are labelled with a fluorescent tracer. After washing off excess labelled antibody molecules, the sample (usually in a microscope slide) is illuminated with light absorbed by the fluorescent tracer. The cells containing the antigen will show the characteristic fluorescence of the tracer.
In cell-free serum, one has to separate the formed antigen-antibody complex from the rest of the serum and the excess reagents, and then measure the concentration of the labelling agent, which should be proportional to the original concentration of the antigen (or antibody). Very often a clinically significant concentration is so small that radioactive tracer methods are employed. The most used radioactive tracer is Iodine 125 (I.sup.125), a gamma emitting isotope of Iodine.
One method for detecting hepatitis associated antigen (HAA) uses a polystyrene tube that has a coating of an unlabelled specific antibody molecules on its inner walls. Next, a serum containing the HAA is incubated in the tube for several hours. Next, the tube is washed. The HAA particles are trapped by the unlabelled antibody molecules. Next, the tube is incubated with a solution containing the specific antibody molecules with Iodine 125 attached thereto. The radioactive specific antibody molecules attach to the HAA particles and form a structure in which the HAA particles are sandwiched between an unlabelled molecule and a labelled radioactive molecule. Then, the tube is washed to remove excess labelled molecules. Finally, the tube is placed within a radioactivity counter for determining the HAA content of the test serum, the number of gamma counts being proportional to the number of HAA particles contained in the test serum sample. In U.S. Pat. No. 3,896,218, S. E. Charm discloses a method of determining the hepatitis associated antigen content of blood using immobilized HAA particles and a radioactive labelled antibody.
Present methods and apparatuses for measuring minute quantities of antigens, antibodies and other substances suffer from the disadvantages that the instrumentation required is relatively complex, the time consumed for such measurements is lengthly, and some radioactive labelled compounds decay too quickly. A need has arisen for methods and apparatuses which can rapidly and accurately measure minute quantities of antigens, antibodies and other substances using relatively simple instrumentation.